The invention relates to a low pressure alarm assembly and, more particularly, to a low pressure alarm assembly incorporating an electrical alarm switch which is activated through a link assembly and pressure indicator operably coupled to a pressure sensing tube.
Oxygen tanks are used in respiratory therapy applications where central oxygen systems are not accessible or available. The oxygen supplied by these tanks is typically regulated to about 50 PSI with a standard regulator/gauge manifold. The pressure in these oxygen tanks is typically about 3000 PSI when full but naturally drops during use as the oxygen is consumed from the tank. One of the problems associated with the use of a simple regulator/gauge manifold is the obvious potential patient hazard that results when the tank runs dry without notice. This problem is particularly common in noisy hospital or clinic environments where, due to the relatively quiet delivery of the oxygen, a tank may run out of oxygen without being noticed.
One device which causes the activation of an alarm when the pressure in the tank falls below a predetermined level is disclosed in U.S. Pat. No. 3,593,582 where the alarm assembly includes two separate pressure sensing members, i.e., a bourdon type gauge or tube operably associated with a pressure indicator and a bellows type gauge associated with an electrical switch actuable to activate a low pressure alarm. A disadvantage associated with this device however is that it requires two separate pressure sensing members, i.e., one which is used in connection with an indicator to measure the pressure and another which is operably associated with a switch to activate the alarm.
The present invention provides an improved low pressure alarm assembly including only one pressure sensing member and where the electrical switch adapted to activate the low pressure alarm is directly operably associated with a link assembly and the pressure indicator associated with the pressure sensing member.
The present invention also provides an improved low pressure alarm incorporating an electrical circuit which allows a visual and/or audible alarm to be tested either prior to or during use of the assembly. Further, an on-off switch allows the alarm to be disabled following activation.
A low pressure alarm assembly of the present invention includes a pressure gauge having a housing, a pressure-responsive element in the housing and adapted for communication with a fluid pressure source, a calibrated dial plate mounted in the housing, a pointer operably associated with the pressure-responsive element and mounted in the housing to sweep the dial plate in response to pressure change in the fluid pressure source, and an alarm assembly in the housing and including an alarm energization circuit with a normally open switch. In accordance with one embodiment of the invention, the pointer is positioned to close the normally open switch when pressure of the fluid pressure source is at a predetermined level.
In one embodiment of the present invention, the pointer is part of the alarm energization circuit. In another embodiment, the pointer is separate from the alarm energization circuit and energizes a switch such as, for example, a proximity switch mounted in the dial plate at a predetermined location.
A linkage assembly, also in the housing, operably couples the pressure-responsive element which, in one embodiment, is a pressure sensing tube to the pointer which sweeps the dial plate. In accordance with one embodiment of the invention, the alarm assembly is operably coupled to the linkage assembly and is actuable in response to the predetermined movement of the linkage assembly to activate a low pressure alarm.
In another embodiment, the alarm assembly switch has first and second contacts which extend outwardly through the plate of the housing, the pointer is separate from the alarm energization circuit, and the pointer is adapted to abut and force the second contact into abutting relationship with the first contact for closing the switch and activating the alarm in response to the movement of the pointer to a predetermined low pressure marking.
The first contact may take the form of a tube extending through the housing and defining an opening in the plate and the second contact may take the form of an elongate wire extending through the tube and terminating in an end protruding through the opening defined in the tube.
In another embodiment, the linkage assembly includes a lever arm which is operably associated with the closed end of the pressure sensing tube and moves in response to the movement of the pressure sensing tube and the alarm assembly includes a proximity switch having a contact operably associated with the lever arm and adapted to shift between open and closed switch positions in response to the movement of the lever arm.
The low pressure alarm assembly of the present invention also includes an alarm housing which houses audible and/or visual alarms which are operably associated with a battery which is operably associated with the switch.
A test switch associated with the alarm housing is operably electrically associated with the audible alarm, the visual alarm and the battery to allow the alarm to be tested both prior to and during use of the assembly.
Further, an on/off switch is associated with the alarm housing and is operably electrically connected to the audible alarm, the visual alarm, the switch and the battery to allow the alarm to be turned off following activation.
Other advantages and features of the present invention will be more readily apparent from the following detailed description of the preferred embodiments of the invention, the accompanying drawings, and the appended claims.